semianaerobic

The story

1. Proto-Indo-European*sem-
2. Proto-Indo-European*sēmi
3. Latinsēmi-
4. Englishsemi-
5. Proto-Indo-European*né
6. Proto-Indo-European*n̥-
7. Proto-Hellenic*ə-
8. Ancient Greekᾰ̓- (ă-)
9. Ancient Greekἀν- (an-)
10. Proto-Indo-European*h₂ews-
11. Proto-Indo-European*h₂ewsér
12. Proto-Hellenic*auhḗr
13. Ancient Greekᾱ̓ήρ (āḗr)
14. Proto-Indo-European*gʷeyh₃-
15. Ancient Greekβῐ́ος (bĭ́os)
16. Frenchanaérobie
17. Englishanaerobic
18. English todaysemianaerobic

From semi- + anaerobic.